In my U.S. Pat. Nos. 5,309,893 and 5,592,932, the contents of which are incorporated herein by reference. I disclose radiant energy collecting apparatus for collecting and concentrating radiant solar energy from the sun. In that apparatus, the solar energy concentrators comprise a plurality of strip mirrors which are arranged along a parabolic curve to define a composite parabolic trough. The mirrors are supported on a buoyant body which may be rotated to follow the sun during the course of the day so as to ensure efficient energy concentration. The buoyant body also support solar energy collectors for collecting the solar energy concentrated by the solar energy concentrators.